Face conveyors with entrainment means attached to conveyor chains have been used for decades in underground mining in order to remove material that has been extracted at a working face by means of an extracting machine, for example a shearer loader or an extracting plough, away from the extracting face and then discard it onto a so-called entry conveyor, which can consist, in particular, of a belt conveyor with circulating rubber belts.
A scraper chain conveyor is used as face conveyor for numerous applications in this connection, said scraper chain conveyor being provided with trough portions which are located one above another and in which the conveyor chains with the connected scraper webs as entrainment means circulate. The upper trough portion is then called the upper run and forms the outward run, whilst the lower run forms the return run. In the majority of cases the scrapers are guided with their scraper ends on profiled side profiles of the trough element. A disadvantage of this development is that the broken material has to be conveyed from the extracting machine into the upper outward run, for which purpose attaching a loading ramp to the side cheek of the trough element on the working face side has been proposed, for example in WO 03/091 541 A1, said side cheek being provided with an angular portion over its height.
Scraper chain conveyors are suitable in particular as face conveyors for extraction plants at longwall faces where face lengths of between 100 and in excess of 400 meters predominate and a migratory support system consisting of numerous shield-type support frames is used. The support shields are located side by side in order to keep the excavation area behind a face front open for the extraction machine, and by advancing the support shields in groups or in turn, the support system is displaced as the face front is excavated further with each operating cycle of the machine.
For special applications such as shortwall extracting, which is used, for example, to advance the machine prop unit (cf. DE 1 583 039), or when material is to be conveyed using both runs (DE 914 478), using the two runs not one above the other but essentially side by side is known.